1. Field of the Invention
The present invention relates to a method of dyeing a high heat-resistant synthetic fiber material. More particularly, the present invention relates to a method of dyeing a high heat-resistant synthetic fiber material at an enhanced leveling and in a high dye-adsorption so as to provide a dyed fiber material having a significantly improved washing fastness.
2. Description of the Related Art
It is well known that synthetic fiber materials, for example, fabrics, are employed not only for various types of clothes but also for various types of industrial materials. Almost all of the synthetic fiber materials are colored. Also, a major portion of the colored fiber materials are produced by dyeing the fiber materials with a dye, whereas a minor portion of the colored fiber materials are produced from synthetic polymer material mixed with a pigment.
Further, it is known that the synthetic fiber material having a high heat-resistant, for example, wholly aromatic polyamide (aramid) fibers, wholly aromatic polyester fibers, polyetheretherketone (PEEK) fibers, polyphenylenesulfide (PPS) fibers, polyethersulfone (PPS) fibers, polyethersulfone (PES) fibers and polyetherimide (PEI) fibers, have a dense fiber structure and thus are very difficult to dye with a dye in a usual dyeing manner. Therefore, the high heat-resistant synthetic fiber materials are usually employed only as industrial materials. In other words, a high degree of difficulty in dyeing is one of the reasons that the high heat-resistant synthetic fiber materials cannot be used for clothes.
To reduce the difficulty in dyeing, JP-A-52-25,178 provides a new method in which an aramid fiber material is pretreated with an organic polar solvent, for example, dimethyl sulfone, and then dyed with a dye. Also, JP-A-62-268,877 provides a new method in which an aramid fiber material is dyed with a dye, which being heated in an organic polar solvent. Further, JP-A-2-99,674 discloses a new high temperature dyeing method in which a polyetherimide (PEI) fiber material is dyed at a temperature of 135.degree. C to 140.degree. C. The above-mentioned new methods are unsatisfactory in that the dye can be adsorbed only in the surface portions of the fibers and thus in the form of a ring, and the dyed fiber material exhibits a poor washing fastness. Also, when the organic polar solvent is employed, the waste water discharged from the dyeing process pollutes the environment.
JP-A-63-256,765 discloses a dyeing method in which an aramid fiber material is dyed with a dye in a vacuum, under which the aramid fibers are swollen.
JP-A-1-111,014 and JP-A-2-41,414 discloses a dyeing method in which a dye or pigment is dispersed in a spinning dope solution of an aramid polymer and this dye or pigment-colored dope solution is subjected to a wet spinning process.
JP-A-3-76,868 discloses a process for producing a poly(p-phenylene-terephthalamide) (PPTA) fiber capable of being dyed with cationic dyes, by immersing a PPTA fiber in an aqueous sulfuric acid solution and then bringing the sulfuric acid-treated PPTA fiber into contact with a specific dyeing promoter.
The above-mentioned methods are unsatisfactory in that they can be utilized only for a limited color range, the reproducibility in dyeing is poor and the light fastness of the dyed fiber material is low.
U.K. Patent No. 1,244,255 discloses a method of drying a heat-resistant fiber material with a disperse dye in an aqueous dyeing medium at a high temperature of 170.degree. C. to 260.degree. C. In this method as disclosed, a disperse dye having a low molecular weight of 314 or less was employed to enhance dye adsorption by the fiber material. This method is, however, disadvantageous in that the dye adsorbed by the fiber material is easily removed by washing and readily faded by light, namely the dyed fiber material exhibits a poor washing fastness and light fastness.